As described in particular in the patents U.S. Pat. Nos. 4,712,818, 4,583,910, 5,117,611, FR 2,494,214, NL 7708236 . . . , the current packing devices intended for the automatic filling of containers by means of superposed layers of products, in particular fruits such as oranges, comprise mainly:                means for transporting the products which are capable, from a flow of products delivered in bulk, of dividing this flow into two separate streams,        two separate feed stations adapted to arrange each stream of products so that the said products are aligned one behind the other in parallel rows, the products of each row, at one feed station, being disposed in alternate positions with respect to the products of the corresponding rows of the other feed station,        a central packing station having means for positioning each container which are capable of holding the said container for the purpose of filling it,        pickup means capable of picking up alternately, in line with each feed station, a number of products forming a layer with dimensions matching the internal section of the container, and of depositing this layer in the said container so as to fill the latter by means of superposed layers of products fixed relative to one another.        
Such packing devices have the advantage of being completely automated and of exhibiting a high filling rate. In addition, the filling of the containers is performed by means of layers of products disposed so as to be perfectly fixed with respect to one another, and the risks of damage to these products, particularly when the latter consist of fruits, during the handling and transport of the containers, are therefore dispelled.
A first major disadvantage of these packing devices resides however in the fact that, in particular at the feed stations, blocking phenomena of the products may lead, if not to immobilisation of the stream of products, at least to the formation of incomplete rows having spaces unoccupied by a product.
Consequently, the filling devices must be subject to constant surveillance, which nevertheless does not prevent the obligation to interrupt the device when blocking phenomena occur.
In particular, the feed stations comprising a plurality of parallel channels, each accommodating a line of products, do not permit the products placed in different lines to be disposed so that they are sufficiently compressed radially against one another to be put in place in a container. This is because a sufficient space must be provided between the channels to permit the displacement of the products in the channels.
To overcome this disadvantage, other devices (for example U.S. Pat. No. 3,453,802) provide that the ends of the channels are offset and the orientation of the pickup means is inclined in the plane of the channels with respect to the channels to form a layer of products in a staggered arrangement. Furthermore, a mechanism enables the lateral flanks of the channels either to be moved apart while they are being fed with products, or to be drawn in to compact the products before they are picked up by the pickup means. This solution requires a mechanism which is extremely complex, costly, unreliable and not very compatible with the agricultural environment in which such devices may move about.
U.S. Pat. No. 3,928,942 or 5,457,933 have proposed another solution consisting of articulated guide plates placed above and at the entrance to the container to compact the products as they fall. But this device lacks efficiency in that it may often produce a dislocation of the layer when the products fall into the container, so that they are not correctly placed in a compacted layer in the container, one or more products being raised with respect to the others.
Furthermore, the presence of the channels considerably increases the risks of blockage of the products at the entrance to each channel.
In view of these problems, the most recent packing devices, as described by U.S. Pat. No. 5,661,949 for example, have feed stations without channels, which are now considered to be incompatible with efficient filling of the containers.
The known packing devices also have another disadvantage resulting from the tiresome operations that have to be carried out when there is a change in the size of products to be packed, which change frequently arises when these products consist of fruits, such as oranges, that are sorted beforehand according in particular to their size. Although certain devices, in particular those described in the U.S. Pat. No. 4,712,818, are equipped with fixing devices permitting the rapid mounting and demounting of a plenum bearing the pickup members, for the purpose of adapting the distribution of these pickup members to the distribution of the products according to their size, the operations for modifying the feed stations are, for their part, tiresome.
The packing device described by U.S. Pat. No. 5,661,949 makes it possible to overcome this second disadvantage as well. In this device, any modification in the size simply requires, on the one hand, the changing of the cradles of the feed stations, this operation being quick and easy given the facility of access to these cradles and, on the other hand, the changing of the support bearing the pickup members. In practice, such an adjustment takes a very short time, which minimises the period of immobilisation of the packing device, and does not require personnel with specific skills. However, such a packing device does not solve the disadvantages associated with the recurrent blocking phenomena of the products.